31121021 has 2 divisors, whose sum is σ = 31121022. Its totient is φ = 31121020.

The previous prime is 31120997. The next prime is 31121039. The reversal of 31121021 is 12012113.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27931225 + 3189796 = 5285^2 + 1786^2 .

It is an emirp because it is prime and its reverse (12012113) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31121021 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31120993 and 31121011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31121081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15560510 + 15560511.

It is an arithmetic number, because the mean of its divisors is an integer number (15560511).

Almost surely, 2^31121021 is an apocalyptic number.

It is an amenable number.

31121021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31121021 is an equidigital number, since it uses as much as digits as its factorization.

31121021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 31121021 is about 5578.6217832006. The cubic root of 31121021 is about 314.5463226354.

Adding to 31121021 its reverse (12012113), we get a palindrome (43133134).

The spelling of 31121021 in words is "thirty-one million, one hundred twenty-one thousand, twenty-one".